The field of art to which this invention is directed is modified thermoplastic copolyester elastomers.
Segmented thermoplastic copolyester elastomers, which contain recurring polymeric long chain ester units derived from phthalic acids and long chain glycols and short chain ester units derived from phthalic acids and short chain glycols, are described in such patents as U.S. Pat. Nos. 3,651,014, 3,763,109 and 4,355,155.
Blends of segmented thermoplastic copolyester elastomers and polyvinyl chloride are described in U.S. Pat. No. 3,718,715.
In U.S. Pat. No. 3,835,098, a process is described for improving the thermal and hydrolytic stability of copolyester elastomers by reacting the elastomer with substantially linear polycarbodiimides having an average of at least two carbodiimide groups per molecule.
Blends of copolyester elastomers, ethylene/carboxylic acid copolymers and polycarbodiimides are described in U.S. Pat. No. 3,963,801.
The thermal-stabilization of copolyester elastomers with guanidines, such as 1,6-hexamethylene-dicyandiamide, is described in U.S. Pat. Nos. 4,520,148, 4,520,149 and 4,520,150.
In many applications, e.g., constant velocity boots used in front-wheel drive automobiles, there is a need for elastomeric compositions which can stand extended contact with hot grease without losing strength and elastomeric properties.